PNG (Portable Network Graphics) Specification, Version 1.2

Status of this Document

This is a revision of the PNG 1.0 specification, which has been
published as RFC-2083 and as a W3C Recommendation. The revision
has been released by the PNG Development Group but has not been
approved by any standards body.

The PNG specification is on a standards track under the purview
of ISO/IEC JTC 1 SC 24 and is expected to be released eventually
as ISO/IEC International Standard 15948. It is the intent of the
standards bodies to maintain backward compatibility with this
specification. Implementors should periodically check the PNG
online resources
(see Online Resources)
for the current status of PNG documentation.

Abstract

This document describes PNG (Portable Network Graphics), an
extensible file format for the lossless, portable, well-compressed
storage of raster images. PNG provides a patent-free replacement for
GIF and can also replace many common uses of TIFF. Indexed-color,
grayscale, and truecolor images are supported, plus an optional alpha
channel. Sample depths range from 1 to 16 bits.

PNG is designed to work well in online viewing applications, such as
the World Wide Web, so it is fully streamable with a progressive display
option. PNG is robust, providing both full file integrity checking and
simple detection of common transmission errors. Also, PNG can store
gamma and chromaticity data for improved color matching on heterogeneous
platforms.

This specification defines the Internet Media Type
"image/png".

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